1. Memorial Park Detention Basin Project
STAKEHOLDERS’ MEETING
Saturday November 3, 2012 – 9:00 AM

2. 1. Introductions

3. 2. San Anselmo is prone to flooding.
Intense rainfall in the watershed
Shallow soils
Steep slopes
3 Large floods have occurred in the last 60 years:
1955
1982
2005

4. Historical Flooding

6. 3. OVERVIEW Ross Valley Flood Control and Watershed Program

7. Throughout the watershed, floods recapture portions of the floodplain.
Source: Stetson Technical Memo No. 1: Existing Conditions Analysis.

8. Methods Methods to reduce flooding:
Increase flow capacity through improvements in the channel
Collect floodwaters using detention basins 8

9. 9

10. Five Sites Were Evaluated

11. Lefty Gomez is Designed to be Compatible with Existing Play Field

12. Lefty Gomez is Designed to be Compatible with Existing Play Field (continued)

13. Flood Water Collection in Phoenix Lake is Enhanced by Increasing Storage Capacity

14. All Detention Basins Combined Reduce 100-Year Peak Flow in Ross by 1,303 cfs

15. Detentions Basins Will Be Used Only For Large Floods
Hypothetical Historical Filling of Basins
Flood Event       Filling of Basin
Partly Full
Full
Partly Full
Partly Full
Full

16. 4. What is a Detention Basin?
A detention basin is a stormwater collection facility which is typically adjacent to a creek or river and is used to store water for limited periods of time-They are often called “dry ponds.”
Parks are common places to use as detention basins.
Detention Basin Examples

17. Hiram Lewis Community Park, Windsor
Homes Adjacent
To Detention Basin/Park
Soccer Field
Baseball Field
Tennis Courts

19. 5. Why Memorial Park was chosen as a potential site
Upstream of flooding
A creek goes through it
Geography
Public land

20. Memorial Park

21. Questions